How is the plaster made?

The hard plaster you are talking about should be black plaster, which is made by weighing the required Chinese medicinal ingredients, soaking them in sesame oil, decocting them in medium fire, and filtering the medicinal oil when the surface of the medicinal materials is dark brown and the inside is dark yellow. Boil the medicinal oil until it drops into beads, and then stir-fry the cream. After adding the cream, continue to boil the oil until the viscous oil drops into the water, and the small oil beads do not touch the hands. Finally, slowly pour it into cold water, stir it, and finally spread it on the plaster skin to make plasters with different specifications.